Swimmer's itch

Swimmer's itch is an itchy rash that can occur after you go swimming or wading outdoors. Also known as cercarial dermatitis, swimmer's itch is most common in freshwater lakes and ponds, but it occasionally occurs in salt water.

Swimmer's itch is an allergic reaction to microscopic parasites that burrow into your skin. The parasites associated with swimmer's itch normally live in waterfowl and some animals that live near the water. Humans aren't suitable hosts, so the parasites soon die while still in your skin.

Although uncomfortable, swimmer's itch is usually short-lived. The rash typically clears up on its own within a few days. In the meantime, you can control itching with over-the-counter or prescription medications.

Swimmer's itch

The itchy rash associated with swimmer's itch looks like reddish pimples or blisters. It may appear within minutes or days after swimming or wading in infested water.

Swimmer's itch usually affects only exposed skin — skin not covered by swimsuits, wet suits or waders. Signs and symptoms of swimmer's itch typically worsen with each exposure to the parasites.

When to see a doctor

Talk to your doctor if you have a rash after swimming that lasts more than one week. If you notice pus at the rash site, consult your doctor. You might be referred to a doctor who specializes in skin conditions (dermatologist).

Swimmer's itch

The parasites that cause swimmer's itch live in the blood of waterfowl and in animals that live near ponds and lakes. Examples include:

Geese

Ducks

Gulls

Beavers

Muskrats

The parasite's eggs enter the water via their hosts' feces. Prior to infecting birds, animals or people, the hatched parasites must live for a time within a type of snail. These snails live near the shoreline, which explains why infections occur most often in shallow water.

Swimmer's itch isn't contagious from person to person, so you don't need to worry about catching swimmer's itch from someone who has this itchy rash.

The more time you spend in infested water, the higher your risk of swimmer's itch. Children may have the highest risk, since they tend to play in shallow water and are less likely to dry off with a towel.

Some people are more sensitive to swimmer's itch than others are. And, your sensitivity can increase each time you're exposed to the parasites that cause swimmer's itch.

You're likely to start by seeing your family doctor or a general practitioner. However, in some cases when you call to set up an appointment, you may be referred immediately to a specialist in skin conditions (dermatologist).

What you can do

Before your appointment, you might want to write a list of answers to the following questions:

Swimmer's itch typically clears up on its own within a few days, though in some cases the rash can last up to a week. In the meantime, you can control itching with over-the-counter antihistamines or anti-itch creams, such as those that contain calamine lotion. If the itching is severe, your doctor may recommend a prescription medication.

Choose swimming spots carefully. Avoid swimming in areas where swimmer's itch is a known problem or signs warn of possible contamination. Also avoid swimming or wading in marshy areas where snails are commonly found.

Avoid the shoreline, if possible. If you're a strong swimmer, head to deeper water for your swim because you may be more likely to develop swimmer's itch if you spend a lot of time in shallow water.

Rinse after swimming. Rinse exposed skin with fresh water immediately after leaving the water, then vigorously dry your skin with a towel. Launder your swimsuits often. You might even alternate wearing different swimsuits.

Skip the bread crumbs. Don't feed birds on docks or near swimming areas.